Two Florida healthcare workers who came in contact with a confirmed Mers case and began showing flu-like symptoms have tested negative for the virus.

But hospital officials are still awaiting test results from 18 health care workers from two Orlando hospitals who are being monitored for symptoms.

On Monday, the second US case of Middle East respiratory syndrome (Mers) was confirmed.

The virus has killed at least 145 people elsewhere

The two confirmed "imported cases" had been both healthcare workers from Saudi Arabia, the country where most of the deaths have occurred.

Health officials say Mers only appears to spread through close contact, but there is no known cure.

Risk to US 'low'

Hospital officials in Orlando told reporters the second confirmed US case had made a visit to the Orlando Regional Medical Center last week, but only to accompany another person having a medical procedure.

What is Mers?

It's a type of coronavirus

These cause respiratory infections in humans and animals

Symptoms include fever, cough and breathing difficulties

It can cause pneumonia and sometimes kidney failure

Experts believe the virus is not very contagious

They are unclear on the best treatment but advise good hand hygiene to prevent transmission